Me: “OK, but it looks like you’ve been using the key for a long time. It must have worked.”

Customer: “Well it did work, but I sold the car and I don’t need it anymore, so I want my money back.”

Me: “Well, I’m sorry sir, but we sell keys; we do not rent them. When you sell the thing the keys fit in, you either give the keys to the new owner or toss them. And even if we did rent keys, the rent for two years would be more than the purchase cost–so actually you would owe us money.”